Wire delay line comprising two transducers, one relatively moveable with respect to the other



3,283,270 ONE RELATIVELY THER E. A. KELLER Nov. 1, 1966 WIRE DELAY LINECOMPRISING TWO TRANSDUCERS MOVEABLE WITH RESPECT TO THE 0 2 Sheets-Sheet1 Filed Feb. 10, 1964 INVENTOR. JFrnes Z @ffeZLeY," BY

Z MI/ 4 Nov. 1 1966 E A. KELLER 3,283,270

WIRE DELAY LINE COMPRISING TWO TRANSDUCERS, ONE RELATIVELY MOVEABLE WITHRESPECT TO THE OTHER Filed Feb. 10, 1964 2 Sheets-Sheet 2 7 INVENTOR.5772655 (2/1 elder, 5%

United States Patent 3 283 270 WIRE DELAY LINE ONlPRISlNG TWt) TRANS-DUCERS, ONE RELATIWELY MQVEABLE WITH RESPECT TO THE OTHER Ernest A.Keller, Wilmette, lll., assignor t0 Motorola, Inc,

Franklin Park, ill, a corporation of Illinois Filed Feb. 10, 1964, Ser.No. 343,520 4 Claims. (Cl. 333-30) This invention relates to a variabledelay line in which the delay is accomplished by propagating a pressurewave in a wire, and in particular to means for variably spacing inputand output transducers with respect to each other, which permits veryclose spacing to provide short minimum delay times, and wherein energyis coupled between the transducers only through the delay in line wire.

In many electrical devices it is desirable to delay signals for periodsof times longer than feasible using purely electrical circuits. One wayin which this has been accomplished has been to introduce a pressurewave, corresponding to the electrical signal to be delayed, into a wireby means of an electromagnetic transducer. A second electromagnetictransducer coupled to the wire receives the pressure wave and generatesan electric signal therefrom. Since the propagation of the pressure wavealong the wire is considerably slower than the propagation of anelectric signal, large time delays can be developed in this manner.

This system works well for relatively long time delays in which thereceiving and transmitting transducers are spaced relatively far apart.However, when it is desired to produce a short time delay using thismethod, energy from the transmitting transducer can be coupled to thereceiving transducer through the magnetic field produced by thetransmitting transducer. Since the time of transmission from thetransmitting transducer to the receiving transducer by means of themagnetic field is considerably shorter than the desired delay, thesignal at the receiving transducer will be distorted and errors in thetime delay can result. Thus the minimum delay time possible isrestricted to a time corresponding to a distance which avoids magneticcoupling between the transducers. This distance is considerably greaterthan the physical dimensions of the electromagnetic transducer wouldpermit, even if proper magnetic shielding between the transducers isused.

Accordingly, it is an object of this invention to provide an improvedvariable delay line which is effective to provide delays of signalsextending over a wide range from short delays to very long delays.

Another object of the invention is to provide electrical delay apparatushaving input and output tranducers coupled to a wire in which a pressurewave is propagated to produce a delay, and in which energy istransferred between the transducers only through the medium of the delayline Wire.

A feature of this invention is the provision of a variable delay linehaving receiving and transmitting transducers and in which thetransmitting transducer operates on a different physical principle thanthe receiving transducer to isolate the same from each other.

Another feature of this invention is the provision of a variable delayline including transmitting and receiving transducers coupled to a wirewhich delays the wave applied thereto, in which one of the transducersis a magnetostrictive device and the other transducer is either apiezoelectric, mechano-resistive or mechano-optical device.

The invention is illustrated in the drawings wherein:

FIG. 1 is a drawing of a variable delay line structure;

FIG. 2 is a cross sectional View of the structure shown in FIG. 1;

FIG. 3 is an enlarged view illustrating the relationship between theinput and output transducers and the delay line wire;

3,283,270 Patented Nov. 1, 1966 FIG. 4 illustrates the combination of amagnetostrictive transducer with a mechano-resistive transducer; and

FIG. 5 illustrates the combination of a magnet-ostrictive transducerwith a mechano-op-tical transducer.

In practicing this invention a variable delay line is providedconsisting of a hollow cylindrical drum having a spiral rectangulargroove cut on the inside. A delay line wire made from a nickel alloysuch as Elenvar and having magnetostrictive properties is coiled in thegroove to form a helix. An input transducer, consisting of a coil ofwire wound around a hollow cylindrical jewel through which the delayline wire passes, is moved along the inside surface of the drum. As theinput transducer is moved along the inside surface of the drum, thedelay line wire is removed from the groove, passes through the jewel andis returned to the groove. Electrical signals coupled to the inputtransducer cause it to generate a magnetic field which develops apressure wave in the delay line wire using magnetostrictive principles.This pressure wave is propagated along the delay line wire until itcontacts a receiving transducer. The receiving transducer can be acrystal device operating upon the piezoelectric or mechano-resistiveprinciples, or a mechano-optical device. The receiving transducerconverts the pressure wave applied thereto to an electrical signalcorresponding to the input electrical signal but delayed in time.

Since the receiving transducer and the transmitting transducer operateon different physical principles, the transmitting transducer can beplaced in close proximity to the receiving transducer without couplingenergy directly to the receiving transducer. If, for example, thereceiving transducer were a second coil of wire operating upon themagnetostrictive principle, undesired coupling through the magneticfield would be possible. By using transmitting and receiving transducershaving different physical principles the energy applied to thetransmitting transducer is coupled to the receiving transducer onlythrough the delay line wire and it is possible to place the twotransducers in close proximity thereby achieving very short delay times.

A delay line incorporating the features of this invention is shown inFIGS. 1 and 2. Similar portions of the two figures have the sameidentifying numerals. The delay line includes a circular drum 21 havinga rectangular spiral groove 24 on the inside surface. A delay line wire22 formed of a nickel alloy such as Elenvar and having magnetostrictiveproperties, rests within the groove forming a helix. An end plate 23 issecured to drum 21 and supports a threaded rod 27 centrally positionedwithin drum 21. One end of an arm 26 is threaded on rod 27 while theother end of arm 26 supports a transmitting transducer 24-. The pitch ofthe threads or rod 27 is the same as the pitch of spiral groove 20 sothat as arm 26 is rotated the end of arm 26 supporting transducer 24advances along the inside surf-ace of drum 21 with transducer 24 alwaysopposite groove 20. Arm 26 is rotated by rod 28 which passes throughopening 19 in arm 26. Rod 28 is connected to an external shaft 29 by arm18. Shaft 29 is mounted on end plate 25 which is secured to drum 21.Rotating shaft 29 causes arm 26 to rotate and move transducer 24 alongthe surface of drum 21. Transducer 24 is connected to amplifier 39through cable 34, slip rings 35 and 37 and cable 38. A piezoelectricreceiving transducer 30 is rigidly fixed to delay line wire 22.

An enlarged view of arm 26, transmitting transducer 24, and receivingtransducer 30 is shown in FIG. 3. The transmitting transducer 24consists of a hollow cylindrical jewel 31 through which the delay linewire 22 passes. Jewel 31 provides a bearing surface for delay line wire22. A coil of wire 32 is wound around bearing 31 and is coupled to asource of electrical signals by wires 41. An electrical signal appliedto the coil of wire 32 generates a magnetic field which imparts apressure wave to the delay line wire 22 by means of the magnetostrictiveeffect. A rnu-metal shield 33 is provided to minimize the external fieldproduced by coil 32.

A receiving transducer 30 consisting of a hollow cylindricalpiezoelectric crystal surrounds delay line wire 22. The crystal ismechanically and electrically bonded to delay line wire 22. The pressurewave received by transducer 30 deforms the crystal and thereby producesan electrical output signal. This signal is coupled to an outputamplifier by means of wires 36.

In operation an input signal to be delayed is applied to transmittingtransducer 24 from amplifier 39. The signal applied to transducer 24creates a pressure wave in delay line wire 22 by means of themagnetostrictive effect. This pressure wave is propagated along delayline wire 22 to the receiving transducer 30 where it is converted to anoutput signal, corresponding to the input signal, by transducer 30 usingthe piezoelectric effect. The delay duration between the input andoutput signals is determined by the length of wire 22 extending betweentransmitting transducer 24 and receiving transducer 30.

FIG. 4 illustrates a second embodiment of this invention in whichtransmitting transducer 24 operates on the magnetostrictive principlewhile the receiving transducer 42 can be a strain gauge operating on themechanoresistive principle. An input signal applied to magnetostrictivetransducer 24 provides a pressure wave in delay line wire 22 asdescribed above. The pressure wave is propagated along delay line wire22 to the receiving transducer 42. The pressure wave distorts thereceiving transducer 42 thereby changing its resistance and causing thecurrent flowing through the transducer to change. The current change intransducer 42 produces an output signal corresponding to the inputsignal but delayed in time. This output signal is coupled to an outputamplifier by means of wire 40. Again, since the transmitting andreceiving transducers operate by different physical principles energy isnot coupled between them directly but only by means of'delay line wire22 connecting the two transducers.

FIG. 5 shows another embodiment of this invention in which thetransmitting transducer 24 is a device operating upon themagnetostrictive principle while the receiving transducer 43 operates onthe mechano-optical principle. Receiving transducer 43 consists of areflecting mirror 46 mechanically connected to delay line wire 22.Mirror 46 is mounted on a torsion wire welded at right angles to themagnetostrictive wire to transfer the longitudinal mechanical motioninto a rotary motion, used to deflect the right beam from light source50 to photocell 51. Again, since the principles upon which the twotransducers operate is different only energy transmitted through delayline wire 22 can be coupled from the transmitting transducer 41 to thereceiving transducer 43.

Thus a simple variable delay line structure has been shown in whichshort delay times can be obtained by using input and output transducersoperating on diiferent physical principles. The different transducerscan be placed in close proximity to each other without the energy in thetransmitting transducer being coupled to the receiving transducer,except through the delay line wire connecting the two transducers.

I claim:

1. Delay line apparatus wherein a time delay is established betweenfirst and second electnical signals and including in combination, ahollow cylinder having a spiral groove on the inside surface thereof,said groove being substantially rectangular in cross section, a wirelocated within and adjacent to the bottom of said groove and forming ahelix, magnetostrictive transducer means adapted to be 11 93 51 2 19.15; said inside surface, said transducer means including a coil aboutsaid wire, and means for removing a portion of said wire from withinsaid groove, said magnetostrictive transducer means being responsive tothe first electrical signal to develop a stress wave in said removedportion of said wire by means of the magnetostrictive effect,piezoelectric transducer means mechanically coupled to said Wire andresponsive to the stress wave therein to develop the second electricalsignal by means of the piezoelectric elfect whereby energy istransferred with a time delay from said magnetostrictive transducermeans to said piezoelectric transducer means only through said wire.

2. A delay line wherein a time delay between first and second electricalsignals is established by propagating a stress wave along a wire andincluding in combination, magnetostrictive transducer means coupled tothe wire and responsive to the first electrical signal to develop astress Wave within the wire, optical transducer means including a mirrorcoupled to the wire, a light source and a photocell, said mirror beingresponsive to said stress Wave to deflect light from said source to saidphotocell for developing the second electrical signal, means coupled toone of said transducer means for moving the same along the wire relativeto the other of said transducer means, the length of the time delaybetween the first and second electrical signals being determined by thelength of said wire between said transducers.

3. Delay line apparatus wherein a time delay is established betweenfirst and second electrical signals and including in combination ahollow cylinder having a spiral groove on the inside surface thereof,said groove being substantially rectangular in cross section, a wirelocated within and adjacent to the bottom of said groove and forming ahelix, magnetostrictive transducer means adapted to be moved along saidinside surface for removing a portion of said wire from within saidgroove, said magnetostrictive transducer means being responsive to thefirst electrical signal to develop a stress wave in said removed portionof said wire by means of the magnetostrictive effect, mechano-opticaltransducer means mechanically coupled to said wire and responsive to thestress wave therein to develop the second electrical signal by means ofthe mechano-optical effect, whereby energy is transferred with -a timedelay from said first transducer to said second transducer only throughsaid wire.

4. Delay line apparatus wherein a time delay is established betweenfirst and second electrical signals and including in combination ahollow cylinder having a spiral groove on the inside surface thereofsaid groove being substantially rectangular in cross section, a wirelocated within and adjacent to the bottom of said groove and forming ahelix, magnetostrictive transducer means adapted to be moved along saidinside surf-ace for removing a portion of said wire from within saidgroove, said magnetostrictive transducer means being responsive to afirst electrical signal to develop a stress wave in said removed portionof said wire, optical transducer means mechanically coupled to said wireand including a mirror coupled to the wire, a light source and aphotocell, said mirror being responsive to the stress wave within saidwire to deflect light from said source to said photocell for developingthe second electrical signal, whereby energy is transferred with a timedelay from said first transducer to said second transducer only throughsaid wire.

References Cited by the Examiner UNITED STATES PATENTS 1,438,753 12/1922Douglas 338148 2,101,272 12/1937 Scott 33372 3,020,497 2/1962 Argentieriet al. 333-30 HERMAN KARL SAALBACH, Primary Examiner.

A. R. MORGANSTERN, M. NUSSBAUM,

Assistant Examiners.

1. DELAY LINE APPARTUS WHEREIN A TIME DELAY IS ESTABLISHED BETWEEN FIRSTAND SECOND ELECTRICL SIGNALS AND INCLUDING IN COMBINATION, A HOLLOWCYLINDER HAVING A SPIRAL GROOVE ON THE INSIDE SURFACE THEREOF, SAIDGROOVE BEING SUBSTANTIALLY RECTANGULAR IN CROSS SECTION, A WIRE LOCATEDWITHIN AND ADJACENT TO THE BOTTOM OF SAID GROOVE AND FORMING A HELIX,MAGNETOSTRICTIVE TRANSDUCER MEANS ADAPTED TO BE MOVED ALONG SAID INSIDESURFACE, SAID TRANSDUCER MEANS INCLUDING A COIL ABOUT SAID WIRE, ANDMEANS FOR REMOVING A PORTION OF SAID WIRE FROM WITHIN SAID GROOVE, SAIDMAGNETOSTRICTIVE TRANSDUCER MEANS BEING RESPONSIVE TO THE FIRSTELECTRICAL SIGNAL TO DEVELOP A STRESS WAVE IN SAID REMOVED PORTION OFSAID WIRE BY MEANS OF THE MAGENTOSTRICTIVE EFFECT, PIEZOELECTRICTRANSDUCER MEANS MECHANICALLY COUPLED TO SAID WIRE AND RESPONSIVE TO THESTRESS WAVE THEREIN TO DEVELOP THE SECOND ELECTRICAL SIGNAL BY MEANS OFTHE PIEZOELECTRIC EFFECT WHEREBY ENERGY IS TRANSFERRED WITH A TIME DELAYFROM SAID MAGNETOSTRICTIVE TRANSDUCER MEANS TO SAID PIEZOELECTRICTRANSDUCER MEANS ONLY THROUGH SAID WIRE.